This is different from many other projects, which use the default wording in the license to allow GPL v2 or any later version.

This is different from many other projects, which use the default wording in the license to allow GPL v2 or any later version.

−

This means it is unlikely that the kernel will switch to GPL version 3.0

+

This means it is unlikely that the kernel will switch to GPL version 3.0.

+

In September of 2006, a group of Linux kernel developers signed a [http://lwn.net/Articles/200422/ position statement] indicating that they objected to GPL version 3.0 (as then drafted). This further indicates the unlikelyhood of any

In September of 2006, a group of Linux kernel developers signed a [http://lwn.net/Articles/200422/ position statement] indicating that they objected to GPL version 3.0 (as then drafted). This further indicates the unlikelyhood of any

Legal Issues using Linux in embedded projects

The intricacies of using the GPL license have been hashed out repeatedly in many
other forums. [references would be nice for major issues]

Here are some highlights:

Kernel is licensed GPL v2 only

The Linux kernel is licensed under the GNU General Public License, version 2.0 ONLY!

This is different from many other projects, which use the default wording in the license to allow GPL v2 or any later version.

This means it is unlikely that the kernel will switch to GPL version 3.0.

In September of 2006, a group of Linux kernel developers signed a position statement indicating that they objected to GPL version 3.0 (as then drafted). This further indicates the unlikelyhood of any
change of the kernel to the GPL v3 license.

Signed-off-by lines and the DCO

When developers contribute to the kernel, they must provide a "Signed-off-by" line, indicating that they acknowledge the licensing and declare the work (to the best of their knowledge) to be either original, or derivative of something compatible with GPL v2.

Use of kernel header files in user-space

It is allowed to use kernel header files in user space, in order for user-space programs to
interact with the kernel via ordinary system calls. This is allowed without the result
that the user-space program becomes a derivative work of the kernel and therefore subject
to GPL.

In general, use of header files do not create derivative works, although there can be exceptions.
There used to be a lot of attention paid to the amount of code (e.g. number of lines) included
from a header file, but no one seems to care about that these days, and this is almost never
a problem. Richard Stallman has stated that use of header files for data structures, constant
definitions, and enumerations (and even small inlines) does not create a derivative work.
See: http://lkml.indiana.edu/hypermail/linux/kernel/0301.1/0362.html

The user-space use of the kernel header files is expected and ordinary. This explicitly encompasses
non-GPL software using these files, and not being affected by the GPL. In order to calm
fears about using the header files directly, and to prevent leakage of kernel internal information
to user-space (where it might be abused), the mainline kernel developers added an option to the
kernel build system to specifically create "sanitized" headers that are deemed safe for use by
user-space programs, without incurring licensing issues.

These are the "make headers_check" and "make headers_install" targets in the kernel build system.

In general, it is legally safest to use such sanitized headers (that is, headers that have
specifically been stripped of large inline macros or anything not required for user space.)

Note that a different process was used by the developers of the Android operating system, to
sanitize headers for bionic for their system. Their process was developed around the same
time as the mainline header sanitization feature.